A study by UT Southwestern Medical Center researchers published August 1 in Nature reveals new insight into why the most common, deadly kind of brain tumor in adults recurs and identifies a potential target for future therapies. Glioblastoma multiforme (GBM) currently is considered incurable. Despite responding to initial therapy, the cancer almost always returns. GBM is a fast-growing, malignant brain tumor that occurred in 15 percent of the estimated 22,000 Americans diagnosed with brain and nervous system tumors in 2010. The median survival rate is about 15 months, according to the National Cancer Institute.